From ba61dfd69504ec6263a9dee9931d93adeb6f3142 Mon Sep 17 00:00:00 2001
From: Rutger Broekhoff
Date: Mon, 7 Jul 2025 21:52:08 +0200
Subject: Initialize repository

---
 lib/nix/lexer.mll | 315 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 315 insertions(+)
 create mode 100644 lib/nix/lexer.mll

(limited to 'lib/nix/lexer.mll')

diff --git a/lib/nix/lexer.mll b/lib/nix/lexer.mll
new file mode 100644
index 0000000..023d888
--- /dev/null
+++ b/lib/nix/lexer.mll
@@ -0,0 +1,315 @@
+{
+open Core
+open Tokens
+
+exception Error of string
+
+(* Types of curly braces.
+   AQUOTE corresponds to the braces for antiquotation, i.e. '${...}'
+   and SET to an attribute set '{...}'.
+ *)
+type braces =
+  | AQUOTE
+  | SET
+
+let print_stack s =
+  let b = Buffer.create 100 in
+  Buffer.add_string b "[ ";
+  List.iter s ~f:(function
+      | AQUOTE -> Buffer.add_string b "AQUOTE; "
+      | SET -> Buffer.add_string b "SET; "
+    );
+  Buffer.add_string b "]";
+  Buffer.contents b
+
+let token_of_str state buf =
+  match state with
+        | `Start -> STR_START (Buffer.contents buf)
+        | `Mid -> STR_MID (Buffer.contents buf)
+
+let token_of_istr state buf =
+  match state with
+        | `Start -> ISTR_START (Buffer.contents buf)
+        | `Mid -> ISTR_MID (Buffer.contents buf)
+
+(* lookup table for one-character tokens *)
+let char_table = Array.create ~len:94 EOF
+let _ =
+  List.iter ~f:(fun (k, v) -> Array.set char_table ((int_of_char k) - 1) v)
+    [
+      '.', SELECT;
+      '?', QMARK;
+      '!', NOT;
+      '=', ASSIGN;
+      '<', LT;
+      '>', GT;
+      '[', LBRACK;
+      ']', RBRACK;
+      '+', PLUS;
+      '-', MINUS;
+      '*', TIMES;
+      '/', SLASH;
+      '(', LPAREN;
+      ')', RPAREN;
+      ':', COLON;
+      ';', SEMICOLON;
+      ',', COMMA;
+      '@', AS
+    ]
+
+(* lookup table for two- and three-character tokens *)
+let str_table = Hashtbl.create (module String) ~size:10
+let _ =
+  List.iter ~f:(fun (kwd, tok) -> Hashtbl.set str_table ~key:kwd ~data:tok)
+    [
+      "//", MERGE;
+      "++", CONCAT;
+      "<=", LTE;
+      ">=", GTE;
+      "==", EQ;
+      "!=", NEQ;
+      "&&", AND;
+      "||", OR;
+      "->", IMPL;
+      "...", ELLIPSIS
+    ]
+
+(* lookup table for keywords *)
+let keyword_table = Hashtbl.create (module String) ~size:10
+let _ =
+  List.iter ~f:(fun (kwd, tok) -> Hashtbl.set keyword_table ~key:kwd ~data:tok)
+    [ "with", WITH;
+      "rec", REC;
+      "let", LET;
+      "in", IN;
+      "inherit", INHERIT;
+      "if" , IF;
+      "then", THEN;
+      "else", ELSE;
+      "assert", ASSERT;
+      "or", ORDEF ]
+
+(* replace an escape sequence by the corresponding character(s) *)
+let unescape = function
+  | "\\n" -> "\n"
+  | "\\r" -> "\r"
+  | "\\t" -> "\t"
+  | "\\\\" -> "\\"
+  | "\\${" -> "${"
+  | "''$" -> "$"
+  | "$$" -> "$"
+  | "'''" -> "''"
+  | "''\\t" -> "\t"
+  | "''\\r" -> "\r"
+  | "''\\n" -> "\n"
+  | x ->
+    failwith (Printf.sprintf "unescape unexpected arg %s" x)
+
+let collect_tokens lexer q lexbuf =
+  let stack = ref [] in
+  let queue = Stdlib.Queue.create () in
+  let rec go () =
+    match (try Some (Stdlib.Queue.take queue) with Stdlib.Queue.Empty -> None) with
+    | Some token ->
+      (
+        match token, !stack with
+        | AQUOTE_CLOSE, [] ->
+          Stdlib.Queue.add AQUOTE_CLOSE q
+        | EOF, _ ->
+          Stdlib.Queue.add EOF q;
+        | _, _ ->
+          Stdlib.Queue.add token q;
+          go ()
+      )
+    | None ->
+      lexer queue stack lexbuf;
+      go ()
+  in
+  Stdlib.Queue.add AQUOTE_OPEN q;
+  stack := [AQUOTE];
+  lexer queue stack lexbuf;
+  go ()
+
+(* utility functions *)
+let print_position lexbuf =
+  let pos = Lexing.lexeme_start_p lexbuf in
+  Printf.sprintf "%s:%d:%d" pos.pos_fname
+    pos.pos_lnum (pos.pos_cnum - pos.pos_bol + 1)
+
+
+let set_filename fname (lexbuf: Lexing.lexbuf)  =
+  let pos = lexbuf.lex_curr_p in
+  lexbuf.lex_curr_p <- { pos with pos_fname = fname }; lexbuf
+
+}
+
+let nzdigit = ['1'-'9']
+let digit = nzdigit | '0'
+let float = (nzdigit digit* '.' digit* | '0'? '.' digit+) (['E' 'e'] ['+' '-']? digit+)?
+let alpha = ['a'-'z' 'A'-'Z']
+let alpha_digit = alpha | digit
+let path_chr = alpha_digit | ['.' '_' '-' '+']
+let path = path_chr* ('/' path_chr+)+
+let spath = alpha_digit path_chr* ('/' path_chr+)*
+let uri_chr = ['%' '/' '?' ':' '@' '&' '=' '+' '$' ',' '-' '_' '.' '!' '~' '*' '\'']
+let scheme = alpha (alpha | ['+' '-' '.'])*
+let uri = scheme ':' (alpha_digit | uri_chr)+
+let char_tokens = ['.' '?' '!' '=' '<' '>' '[' ']' '+' '-' '*' '/' '^' '(' ')' ':' ';' ',' '@']
+
+rule get_tokens q s = parse
+(* skip whitespeces *)
+| [' ' '\t' '\r']
+    { get_tokens q s lexbuf }
+(* increase line count for new lines *)
+| '\n'
+    { Lexing.new_line lexbuf; get_tokens q s lexbuf }
+| char_tokens as c
+    { Stdlib.Queue.add (Array.get char_table ((int_of_char c) - 1)) q }
+| ("//" | "++" | "<=" | ">=" | "==" | "!=" | "&&" | "||" | "->" | "...") as s
+    { Stdlib.Queue.add (Hashtbl.find_exn str_table s) q}
+| digit+ as i
+    { Stdlib.Queue.add (INT i) q }
+| float
+    { Stdlib.Queue.add (FLOAT (Lexing.lexeme lexbuf)) q }
+| path
+    { Stdlib.Queue.add (PATH (Lexing.lexeme lexbuf)) q }
+| '<' (spath as p) '>'
+    { Stdlib.Queue.add (SPATH  p) q }
+| '~' path as p
+    { Stdlib.Queue.add (HPATH  p) q }
+| uri
+    { Stdlib.Queue.add(URI (Lexing.lexeme lexbuf)) q }
+(* keywords or identifiers *)
+| ((alpha | '_')+ (alpha_digit | ['_' '\'' '-'])*) as id
+    { Stdlib.Queue.add (Hashtbl.find keyword_table id |> Option.value ~default:(ID id)) q}
+(* comments *)
+| '#' ([^ '\n']* as c)
+    { ignore c; get_tokens q s lexbuf}
+| "/*"
+    { comment (Buffer.create 64) lexbuf;
+      get_tokens q s lexbuf
+    }
+(* the following three tokens change the braces stack *)
+| "${"
+    { Stdlib.Queue.add AQUOTE_OPEN q; s := AQUOTE :: !s }
+| '{'
+    { Stdlib.Queue.add LBRACE q; s := SET :: !s }
+| '}'
+    {
+      match !s with
+      | AQUOTE :: rest ->
+        Stdlib.Queue.add AQUOTE_CLOSE q; s := rest
+      | SET :: rest ->
+        Stdlib.Queue.add RBRACE q; s := rest
+      | _ ->
+        let pos = print_position lexbuf in
+        let err = Printf.sprintf "Unbalanced '}' at %s\n" pos in
+        raise (Error err)
+    }
+(* a double-quoted string *)
+| '"'
+    { string `Start (Buffer.create 64) q lexbuf }
+(* an indented string *)
+| "''" (' '+ as ws)
+    { istring `Start (Some (String.length ws)) (Buffer.create 64) q lexbuf }
+| "''"
+    { istring `Start None (Buffer.create 64) q lexbuf }
+(* End of input *)
+| eof
+    { Stdlib.Queue.add EOF q }
+(* any other character raises an exception *)
+| _
+    {
+      let pos = print_position lexbuf in
+      let tok = Lexing.lexeme lexbuf in
+      let err = Printf.sprintf "Unexpected character '%s' at %s\n" tok pos in
+      raise (Error err)
+    }
+
+(* Nix does not allow nested comments, but it is still handy to lex it
+   separately because we can properly increase line count. *)
+and comment buf = parse
+  | '\n'
+    {Lexing.new_line lexbuf; Buffer.add_char buf '\n'; comment buf lexbuf}
+  | "*/"
+    { () }
+  | _ as c
+    { Buffer.add_char buf c; comment buf lexbuf }
+
+and string state buf q = parse
+  | '"'                         (* terminate when we hit '"' *)
+    { Stdlib.Queue.add (token_of_str state buf) q; Stdlib.Queue.add STR_END q }
+  | '\n'
+    { Lexing.new_line lexbuf; Buffer.add_char buf '\n'; string state buf q lexbuf }
+  | ("\\n" | "\\r" | "\\t" | "\\\\" | "\\${") as s
+      { Buffer.add_string buf (unescape s); string state buf q lexbuf }
+  | "\\" (_ as c)               (* add the character verbatim *)
+      { Buffer.add_char buf c; string state buf q lexbuf }
+  | "${"               (* collect all the tokens till we hit the matching '}' *)
+    {
+      Stdlib.Queue.add (token_of_str state buf) q;
+      collect_tokens get_tokens q lexbuf;
+      string `Mid (Buffer.create 64) q lexbuf
+    }
+  | _ as c                  (* otherwise just add the character to the buffer *)
+    { Buffer.add_char buf c; string state buf q lexbuf }
+
+and istring state imin buf q = parse
+  | ('\n' ' '* "''")
+      {
+        Lexing.new_line lexbuf;
+        Buffer.add_string buf "\n";
+        let indent = match imin with | None -> 0 | Some i -> i in
+        Stdlib.Queue.add (token_of_istr state buf) q;
+        Stdlib.Queue.add (ISTR_END indent) q
+      }
+  | "''"
+      {
+        let indent = match imin with | None -> 0 | Some i -> i in
+        Stdlib.Queue.add (token_of_istr state buf) q;
+        Stdlib.Queue.add (ISTR_END indent) q
+      }
+  | ('\n' ' '* '\n') as s
+    {
+      Lexing.new_line lexbuf;
+      Lexing.new_line lexbuf;
+      Buffer.add_string buf s;
+      istring state imin buf q lexbuf
+    }
+  | ('\n' (' '* as ws)) as s
+    {
+      Lexing.new_line lexbuf;
+      Buffer.add_string buf s;
+      let ws_count = String.length ws in
+      match imin with
+      | None ->
+        istring state (Some ws_count) buf q lexbuf
+      | Some i ->
+        istring state (Some (min i ws_count)) buf q lexbuf
+    }
+  | ("''$" | "'''" | "''\\t" | "''\\r" | "''\\n") as s
+      { Buffer.add_string buf (unescape s); istring state imin buf q lexbuf }
+  | "''\\" (_ as c)
+      { Buffer.add_char buf c; istring state imin buf q lexbuf }
+  | "${"
+    {
+      Stdlib.Queue.add (token_of_istr state buf) q;
+      collect_tokens get_tokens q lexbuf;
+      istring `Mid imin (Buffer.create 64) q lexbuf
+    }
+  | _ as c
+    { Buffer.add_char buf c; istring state imin buf q lexbuf }
+{
+
+let rec next_token
+    (q: token Stdlib.Queue.t)
+    (s: braces list ref)
+    (lexbuf: Lexing.lexbuf)
+  : token =
+  match (try Some (Stdlib.Queue.take q) with | Stdlib.Queue.Empty -> None) with
+  | Some token ->
+    token
+  | None ->
+    get_tokens q s lexbuf;
+    next_token q s lexbuf
+}
-- 
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